Hydration and cooling in elite athletes: relationship with performance, body mass loss and body temperatures during the Doha 2019 IAAF World Athletics Championships

Purpose. To characterise hydration, cooling, body-mass loss, and core (Tcore) and skin (Tsk) temperatures during World Athletics Championships in hot-humid conditions. Methods. Marathon and race-walk (20km and 50km) athletes (n=83, 36 women) completed a pre-race questionnaire. Pre- and post-race body weight (n=74), Tcore (n= 56) and Tsk (n= 49; thermography) were measured. Results. Most athletes (93%) had a pre-planned drinking strategy [electrolytes (83%), carbohydrates (81%)] whilst ice-slurry was less common (11%; pConclusion. Most athletes hydration strategies were pre-planned based on personal experience. Ice-vests were the most adopted pre-cooling and the only one minimizing Tcore, suggesting that event organisers should be cognisant of logistic (i.e. freezers). Dehydration was moderate and unrelated to performance. Pre-race Tsk was related to performance and DNF, suggesting that Tsk modulation should be incorporated into pre-race strategies</div

Thermoregulatory responses during road races in hot-humid conditions at the 2019 Athletics World Championships

Purpose: To characterise thermoregulatory and performance responses of elite road-race athletes, while competing in hot, humid, night-time conditions during the 2019 IAAF World Athletic Championships.  Method: Male and female athletes, competing in the 20 km racewalk (n=20 males, 24 females), 50 km racewalk (n=19 males, 8 females) and marathon (n=15 males, 22 females) participated. Exposed mean skin (Tsk) and continuous core body (Tc) temperature were recorded with infrared thermography and ingestible telemetry pill, respectively.  Results: The range of ambient conditions (recorded roadside) were 29.3-32.7°C air temperature, 46-81 % relative humidity, 0.1-1.7 m∙s-1 air velocity and 23.5-30.6°C wet bulb globe temperature. Tc increased by 1.5 ± 0.1°C but mean Tsk decreased by 1.5 ± 0.4°C over the duration of the races. Tsk and Tc changed most rapidly at the start of the races and then plateaued, with Tc showing a rapid increase again at the end, in a pattern mirroring pacing. Performance times were between 3 to 20 % (mean = 113 ± 6%) longer during the championships compared to the personal best (PB) of athletes. Overall mean performance relative to PB was correlated with the wet-bulb globe temperature (WBGT) of each race (R2 = 0.89), but not with thermophysiological variables (R2 ≤ 0.3).  Conclusion: As previously reported in exercise heat stress, in this field study Tc rose with exercise duration, whereas Tsk showed a decline. The latter contradicts the commonly recorded rise and plateau in laboratory studies at similar ambient temperatures, but without realistic air movement.</p